Lactate

A. Indicator of Tissue Hypoxia

Elevated lactate is a key marker of inadequate tissue oxygenation.

Occurs in:

• Shock (hypovolemic, cardiogenic, septic)

• Severe anemia

• Cardiac arrest

• Respiratory failure

Persistent elevation indicates poor prognosis.

B. Sepsis and Septic Shock

Lactate measurement is essential in diagnosing and monitoring Sepsis.

• Lactate ≥ 2 mmol/L → tissue hypoperfusion

• Lactate ≥ 4 mmol/L → severe sepsis / septic shock

• Used to guide resuscitation therapy

C. Lactic Acidosis

Defined as lactate > 4 mmol/L with metabolic acidosis.

Types:

Type A (Hypoxic)

• Shock

• Severe blood loss

• Cardiac failure

Type B (Non-hypoxic)

• Liver disease

• Malignancy

• Drugs (e.g., metformin)

• Inborn errors of metabolism

D. Monitoring Critically Ill Patients

Used in:

• ICU patients

• Trauma cases

• Post-surgical monitoring

• Cardiac arrest resuscitation

Serial lactate levels help assess treatment response.

E. Exercise Physiology

• Intense exercise → increased lactate production

• Used in sports medicine to assess anaerobic threshold

F. Liver Function

Since lactate is metabolized in the liver (Cori cycle), elevated levels may indicate:

• Severe liver dysfunction

• Impaired gluconeogenesis